Environment

Atmospheric CO2 hits 23-million-year peak, plant fossils reveal

Atmospheric CO2 hits 23-millio...
Plant fossils can reveal the levels of carbon dioxide in the atmosphere at the time they lived
Plant fossils can reveal the levels of carbon dioxide in the atmosphere at the time they lived
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Plant fossils can reveal the levels of carbon dioxide in the atmosphere at the time they lived
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Plant fossils can reveal the levels of carbon dioxide in the atmosphere at the time they lived

It’s well known that the current levels of carbon dioxide in the atmosphere are the highest they’ve been in a long time – but is that a few hundred years? Thousands? Millions? According to a new study of fossil plant matter, CO2 concentrations haven’t been this high in at least 23 million years, and have never shot up this fast.

Lately we’ve been breaking a lot of records in terms of atmospheric carbon dioxide levels. In 2016 the South Pole became the last region on Earth to exceed a concentration of 400 parts per million (ppm). In May 2019, the Mauna Loa Observatory in Hawaii picked up a record new high of 415.26 ppm. Currently, levels are the highest they've been in all of human history.

And these are records we really don’t want to be breaking. Higher carbon dioxide levels are linked to climate change, and all the devastation that can bring. Long-term studies have shown a sharp spike from the early 19th century onwards – “coincidentally” right around the time of the Industrial Revolution.

To see just how bad things may be, we need to look to the past. Our direct records go back a few hundred years, but it gets murky before that. Drilled ice cores give us a glimpse as far back as 2.7 million years – and unfortunately, revealed that levels were less than 300 ppm back then.

For the new study, researchers at the University of Louisiana set out to look even further back in time, stretching 23 million years back. The team managed this by examining fossil remains of ancient plants.

When plants grow, they take in carbon dioxide from the atmosphere, and their tissues retain certain stable isotopes of carbon – specifically, carbon-12 and carbon-13. When these plants fossilize, scientists can study the amounts of these isotopes and determine the concentration of CO2 that the plants grew in.

Using this method, the researchers found that throughout this 23-million-year period CO2 levels mostly fluctuated between around 230 ppm and 350 ppm. That’s far less than modern levels. The team also found no increase in that time as sharp as the climb we’re currently experiencing.

Worse still, the most dramatic warming episodes in the last 23 million years were associated with fairly small increases in CO2. That includes the middle Miocene, which occurred between 15 and 17 million years ago, and the middle Pliocene of three to five million years ago.

The new study gives us further evidence of the severity of the challenge we’re now facing (on top of all the other ones, of course).

The research was published in the journal Geology.

Source: The Geological Society of America

8 comments
drBill
It is an interesting article. It might be more interesting if correlation ever meant causation. The 68% CI range was 170-540 ppm, by the way, so the 230-350 ppm range is about the 34% confidence interval, while the 95% confidence interval would include an upper concentration of >700 ppm, reflecting the skew of a non-normal data set. Added to that, the averaging of time-sensitive data is problematic, especially when using it to present data with a pov in mind.
Kpar
That's funny, I have been reading how the current levels of CO2 are many times lower than they have been in the past, and how we may be experiencing a dearth of CO2.

Also, there doesn't seem to be any empirical evidence that CO2 controls planetary temperature- just speculation.
clay
Go drbill! :-)

CO2 and its precipitation is essential for life as we know it. This is why the search for earth-like planets has CO2 in that range as part of the requirements criteria (250ppm-1000ppm or thereabouts)
christopher
We should spend more time debating things we are utterly powerless to change. Oh. wait...
Ron vdS
This fossil leaves look very healthy and like they belong in a rain forest. It's such a pity it has taken us millions of years to get back to a healthy level of CO2 for our planet.
Karmudjun
So much conjecture - and drBill's mad math skills - obscuring the pure science of this article. While causation does not necessarily come from clearly discernible processes which correlate with both historical record and stratospheric findings in a rather tight manner we DO know that halogenated compounds, CO2, Methane, and other 'green house gases' do keep the sun's heat from radiating back out through the stratosphere. Damn NASA for elucidating all these troublesome facts! While our Ozone layer is depleting - and ozone is supposed to be a 'good gas' in the stratosphere - we are not entirely completely indubitably certain that chlorofluorocarbons and other halogenated compounds caused the ozone depletion. After all, there have been ozone depletions in the past and species declination coincidentally at the same time frame of the historical record - again - not causative even though the UV light rapidly screws with DNA and RNA bonds. It sucks that my grandchildren will have to ignore or engage in the scientific developments required to mitigate the environmental degradation that could possibly be happening as the oceans rise, as the 100 year floods happen repeatedly during a score, and as the permafrost thaws releasing even more methane pockets from the
bwana4swahili
"Higher carbon dioxide levels are linked to climate change, and all the devastation that can bring."

Looking forward to the benefits of a bit of global warming and associated rain fall. Many advantages to countries in the northern hemisphere.

Yes, some countries may see devastation but nature's law of 'adapt or die' still applies and homo sapiens are more than capable of adapting as we have for millions of years.
Hosni Mubarak
Denial ain't just a river in Egypt.